O ACIDS BASES AND AQUEOUS EQUILIRIA Identifying the major species in weak acid o
ID: 544486 • Letter: O
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O ACIDS BASES AND AQUEOUS EQUILIRIA Identifying the major species in weak acid or weak base The preparations of two aqueous solutions are described in the table below. For each solution, write the chemical formulas of the major species present at equilibrium. You can leave out water itsef wnte the chemical formulas of the species that wil act as acids in the 'acids row, the formulas of the species that will act as bases in the bases' row, and the formulas of the species that will act as neither acids nor bases in the 'other row You will find iR useful to keep in mind that HCH ,CO2 is a weak acid 11 mol of NaO)H is added to 10 L of a 1.1 M HCH,Co, baes 10 L of asolution that iw 4 BN M control option command command optionExplanation / Answer
(1) 1.1 mole of NaOH is added to 1 L of 1.1 M HCH3CO2 (acetic acid) solution.
Mole(s) of HCH3CO2 present initially = (1 L)*(1.1 M)*(1 mol/L/1 M) = 1.1 mole.
Write down the balanced chemical equation as below.
HCH3CO2 (aq) + NaOH (aq) -------> NaCH3CO2 (aq) + H2O (l)
As per the balanced stoichiometric equation,
1 mole HCH3CO2 = 1 mole NaOH = 1 mole NaCH3CO2
Therefore,
1.1 mole NaOH = 1.1 mole HCH3CO2.
Thus, HCH3CO2 is completely neutralized and the solution contains 1.1 mole NaCH3CO2 (major species). NaCH3CO2 is a base (ans).
(2) Find out the moles of HCH3CO2 and KCH3CO2 present in 1.0 L of the solution.
Moles HCH3CO2 = (1.0 L)*(0.9 M)*(1 mol/L/1 M) = 0.9 mole.
Moles KCH3CO2 = (1.0 L)*(0.9 M)*(1 mol/L/1 M) = 0.9 mole.
Moles KOH added = 0.1 mole.
KOH reacts with HCH3CO2 as below.
KOH (aq) + HCH3CO2 (aq) --------> KCH3CO2 (aq) + H2O (l)
As per the balanced stoichiometric equation,
1 mole HCH3CO2 = 1 mole KOH = 1 mole KCH3CO2
Therefore,
0.1 mole NaOH = 0.1 mole HCH3CO2 neutralized = 0.1 mole KCH3CO2 formed.
Moles HCH3CO2 at equilibrium = (0.9 – 0.1) mole = 0.8 mole.
Moles KCH3CO2 at equilibrium = (0.9 + 0.1) mole = 1.0 mole.
Thus, KCH3CO2 is the major species at equilibrium. KCH3CO2 is a base and HCH3CO2 is an acid.
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